1. Field of the Invention
This invention relates to an optically pumped solid state laser and a method for its manufacture. More particularly, it relates to such a laser which is constructed of components having attached fittings which are structured in such a manner that the components are automatically arranged with respect to one another along an optical path upon joining the fittings together.
2. Description of the Prior Art
During the period of time since the first operating laser was demonstrated in 1960, laser development work has resulted in a wide variety of lasers in terms of size, power, output frequency, active medium (lasant material) and method of excitation. For the most part, these devices can be classified as precision instruments and are typically handmade by skilled craftsmen. Features which such devices share in common include a resonator, a pump source (a source of energy to either create or activate the lasant material), and means for removing heat. Aside from solid state semiconductor laser diodes, such as those based on gallium arsenide and gallium aluminum arsenide, most of the currently available lasers are based on gas-discharge technology and are both large and inefficient. Such gas-discharge technology involves either the direct use of a gas discharge, as in a carbon dioxide laser, or the indirect use of a gas discharge, as in a flash lamp which is used to excite a lasant material.
When the optical components of a laser are relatively far apart (about 15 to 800 cm in conventional lasers), small angular misalignments result in substantial losses in laser output power. Accordingly, laser resonators are designed to ensure the maintenance of a stable orientation of these optical components. This design requirement has dictated the use of highly rigid materials such as Invar, glass, granite, steel and various ceramics for resonator construction.
Heat which is produced as an undesired by-product of laser operation has also placed constraints on the design of laser resonators. Temperature fluctuations produced by such heat result in thermally induced distortions of the resonator and associated misalignment of the optical components within the resonator. Accordingly, conventional laser designs have addressed this problem through the use of materials having a low coefficient of thermal expansion, such as Invar, quartz and various ceramics, and also by using external cooling means to thermally stabilize the resonator.
The use of flashlamps, light-emitting diodes, laser diodes and laser diode arrays to optically pump or excite a solid lasant material is well known. Lasant materials commonly used in such solid state lasers include crystalline or glassy host materials into which an active material, such as trivalent neodymium ions, is incorporated. Conventional host materials for neodymium ion include glass and yttrium aluminum garnet (referred to as YAG). By way of example, when neodymium-doped YAG is employed as the lasant material in an optically pumped solid state laser, it is typically pumped by absorption of light having a wavelength of about 810 nm and emits light having a wavelength of 1,064 nm.
U.S. Pat. No. 3,624,545 issued to Ross on Nov. 30, 1971, describes an optically pumped solid state laser composed of a YAG rod which is side-pumped by at least one semiconductor laser diode. Similarly, U.S. Pat. No. 3,753,145 issued to Chesler on Aug. 14, 1973, discloses the use of one or more light-emitting semiconductor diodes to end pump a neodymium-doped YAG rod. The use of an array of pulsed laser diodes to end pump a solid lasant material such as neodymium-doped YAG is described in U.S. Pat. No. 3,982,201 issued to Rosenkrantz et al. on Sept. 21, 1976. Finally, D. L. Sipes, Appl. Phys. Lett., Vol. 47, No. 2, 1985, pp. 74-75, has reported that the use of a tightly focused semiconductor laser diode array to end pump a neodymium-doped YAG results in a high effeciency conversion of pumping radiation having a wavelength of 810 nm to output radiation having a wavelength of 1,064 nm.
Materials having nonlinear optical properties are well known and have the ability to function as harmonic generators. For example, U.S. Pat. No. 3,949,323 issued to Bierlen et al. on Apr. 6, 1976, discloses the use as second harmonic generators of materials having the formula MTiO(XO.sub.4) where M is at least one of K, Rb, Tl and NH.sub.4 ; and X is at least one of P or As, except when NH.sub.4 is present then X is only P. This generic formula includes potassium titanyl phosphate, KTiOPO.sub.4, a particularly useful nonlinear material. Other known nonlinear optical materials include, but are not limited to, KH.sub.2 PO.sub.4, LiNbO.sub.3, KNbO.sub.3, LiIO.sub.3, HIO.sub.3, KB.sub.5 O.sub.8.4H.sub.2 O and urea. A review of the nonlinear optical properties of a number of different uniaxial crystals has been published in Sov. J. Quantum Electron., Vol. 7, No. 1, January 1977, pp. 1-13.
Nonlinear optical materials can be utilized to frequency double the output radiaton of a solid state laser. For example, it has been reported by R. F. Belt et al., Laser Focus/Electro-Optics, October 1985, pp. 120-121, that potassium titanyl phosphate can be utilized to frequency double the 1,064 nm output of a neodymium-doped YAG laser to afford light having a wavelength of 532 nm.
U.S. Pat. No. 4,526,444 issued to Fantone et al. on July 2, 1985, is directed to a viewfinder assembly which is fabricated virtually exclusively of injection molded plastics. Various optical components of the viewfinder are structured to snap-fit together inside a housing. More specifically, both the lens components and the housing are provided with complementary configured snap-type connectors which allow quick assembly and automatic positioning of the lens components with respect to each other. However, the viewfinder described in this patent is a passive optical system which does not generate light or heat. There is no teaching or suggestion in the patent that the active optical system of an optically pumped solid state laser could be assembled using complementary configured connectors of any type.